In recent years, along with the popularization of a personal computer, a digital camera through which an image can be captures into the personal computer easily is coming into wide use. Further, incorporating a digital camera in an information processing equipment such as a mobile computer, a cell-phone and a personal digital assistant (PDA: Personal Digital Assistant) is now generalized. With this spread of a digital camera, a digital camera in a smaller size is demanded, and a lens unit to be incorporated in this digital camera in a smaller size is required to be further smaller. For photographing, on the other hand, a high-power zoom lens that is easy-to-use is demanded.
To cope with these demands, there is available an image pickup apparatus equipped with an image pickup means that outputs electric signals in accordance with an amount of incident light, including therein: an optical means that bends an optical path of incident light, for example, a reflecting mirror; a first lens group that is constructed at the object side of the reflecting mirror and is driven such that at least a part of the first lens group is housed in the image pickup apparatus when an image is not taken, and that the first lens group is more protruded toward the object side than its housed condition when an image is taken; and a second lens group constructed at the object side of the image pickup means (See Japanese Patent Publication Open to Public Inspection No. 2006-64958). In the image pickup apparatus, the reflecting mirror moves to a position so as to change the optical path of an optical image of an object entering through the first lens group to the direction of the second lens group when an image is taken, and moves from an area where the first lens group is housed to the position for retreating when an image is not taken. Specifically, the Japanese Patent Publication Open to Public Inspection (JP-A) No. 2006-64958 discloses an image pickup apparatus in which a prism is used as an optical means, and the first lens group and the prism retreat integrally in the direction of a thickness of a camera body before image taking is completed. JP-A No. 2006-64958 further discloses, specifically, an image pickup apparatus in which a prism and a second lens group are moved integrally in the optical axis direction of the second lens group representing a lateral direction of a camera body to make a space of retreating for the first lens group.
However, as for the image pickup apparatus described in JP-A No. 2006-64958, the method to retreat the prism and the first lens group integrally in the thickness direction of a camera boy when an image is not taken, provides difficulty of making a camera body thin in its thickness direction in. Further, the method to make an space for the first lens group to retreat by moving the prism and the second lens group integrally in the lateral direction of a camera body, provides difficulty of making a size of the second lens group small in its optical axis direction because it requires to secure the space by making the second lens group in addition to the prism to be retreated. Further, the structure has a complicated structure because it is necessary to move both of the prism and the second lens group.